In general, a vehicle is equipped with a suspension system to improve its ride comfort and road-holding efficiency. The suspension system includes a spring and a shock absorber, i.e., a damper.
Conventionally, the damper is installed in parallel to a spring positioned between a body and a wheel of the vehicle. The damper absorbs vibrations of the vehicle that are caused by an impact on the spring when the vehicle travels. In other words, the damper reduces vertical kinetic energy of the spring so as to improve the ride comfort.
Recently, an increasing number of vehicles use a variable damper capable of controlling the damping force to further improve the ride comfort. In this case, the damping force is controlled by employing a control logic.
A conventional ECS (electronics controlled suspension) system employing such a control logic utilizes a steering angle sensor, a yaw rate sensor, a lateral G sensor, a vehicle speed sensor, a wheel speed sensor, in order to attain an anti-roll control thereby providing steering stability of a vehicle.
However, even though a vehicle uses the ECS system, a driver of the vehicle may experience an under- or over-steering phenomenon in an environment where the road surface is slippery or urgent steering is required. In such a situation, the vehicle may not be steered as the driver desires. Accordingly, in order to prevent such phenomena, an anti-yaw control is required in addition to the anti-roll control.